598 — Scientific Proceedings, Royal Dublin Society. 
upon its surface. A mass of crystals was obtained in this way, 
which were freed from adhering liquid and dried at 100° cent. 
These crystals should, according to Watt’s Dictionary, have the 
formula, HgSO, (SO,),. On treating them with water, they 
changed from a white to a yellow colour, and produced the basic 
salt. On being analyzed, the crystals proved to be wholly com- 
posed of the neutral sulphate, HgSO,,. 
A further quantity of neutral sulphate was decomposed by 
water, the proportion of water used being in the ratio of two 
molecules to four molecules of the sulphate. The basic salt hav- 
ing been separated from the liquid, the latter was allowed to 
evaporate spontaneously in vacuo over sulphuric acid. The crys- 
tals obtained in this way were placed upon a tile and allowed to 
drain during two days. They were pressed between sheets of 
bibulous paper, washed with disulphide of carbon, dried, and 
analyzed. They proved to be crystals of the neutral sulphate. 
Neutral mercuric sulphate was dissolved in dilute sulphuric 
acid, and the mixture allowed to evaporate spontaneously in 
vacuo. The crystals which formed consisted simply of neutral 
mercuric sulphate. 
The action of water upon mercuric sulphate produces a basic 
salt and free sulphuric acid —3HgSO0,+2H,0=HeSO,(Hg0),+ 
2H,SO,. The free acid dissolves some mercuric sulphate, but no 
acid salt appears to exist—at least, it cannot be got out of solution. 
The last crystals that form spontaneously out of the most acid 
solution are composed of the neutral sulphate. 
When a large quantity of water is employed in decomposing 
mercuric sulphate no mercury, or a mere trace, is to be found in 
the liquid when separated from the basic salt. On the other 
hand more mercury remains in solution when three molecules of 
water are used in decomposing the neutral salt than when two— 
the theoretical amount—are employed. The neutral sulphate is 
more soluble in slightly diluted sulphuric acid than in the strong 
acid, but it is not sensibly soluble in very diluted acid. 
It may be worth noting here, that when basic mercuric sul- 
phate is dissolved in selenic acid, and the mixture allowed to 
evaporate spontaneously, neutral mercuric sulphate makes its ap- 
pearance, but when on the contrary, basic mercuric selenate 
HegSeO,(HgO), is dissolved in sulphuric acid, and the solution 
